Relativistic analytical R-matrix (ARM) theory for strong-field ionization

TL;DR

This paper extends the analytical R-matrix (ARM) theory into the relativistic regime to better describe strong-field ionization of highly-charged ions in ultrastrong laser fields, comparing it with existing models.

Contribution

The paper introduces a relativistic generalization of the ARM theory for strong-field ionization, enabling more accurate modeling of highly-charged ions under intense laser fields.

Findings

Relativistic ARM theory provides improved descriptions over nonrelativistic models.

Comparison shows advantages and limitations relative to Coulomb-corrected SFA.

Coulomb enhancement effects are significant at the ionization cutoff.

Abstract

The analytical R-matrix (ARM) theory has been known for an efficient description of the Coulomb effects of the atomic core in strong-field ionization in the nonrelativistic regime. We generalize the ARM theory into the relativistic domain aiming at the application to strong-field ionization of highly-charged ions in ultrastrong laser fields. Comparison with the relativistic Coulomb-corrected strong field approximations (SFA) is provided, highlighting the advantages and disadvantages. The weakly relativistic asymptotics and its accordance with the nondipole Coulomb-corrected SFA are examined. As an example of a physical application of the relativistic ARM, the Coulomb enhancement of tunneling ionization probability for highly-charged ions at the cutoff of the direct channel is discussed.